A command block dispensed from a dispenser onto a block that should power the block is no longer activated when placed

In previous versions, a command block with data tags would activate when dispensed from a dispenser, if that block completed a redstone circuit when placed. For example, a dispenser pointed down above an air block, with a redstone torch on the block below that will not activate in the 14w27b snapshot. This change in behavior breaks a number of redstone machines I'm using in adventure worlds with the snapshot.